1. Field of the Invention
This invention relates to an alloy target which is suitable for use in the manufacture of a magneto-optical recording medium by a sputtering method.
2. Description of the Prior Art
A magneto-optical memory has been drawing an attention that facilitates the erasure and recording of information in recent years, and single-crystal materials such as garnets, polycrystalline materials such as MnBi and PtCo, or amorphous materials such as alloys of rare earth elements and transition metals are known for the material of the magneto-optical memory.
Among them, an amorphous alloy comprising rare earth element and transition metal (Tb-Fe-Co, Gd-Tb-Fe, etc.) provides a variety of advantages, for example, requiring only a small amount of energy for recording, free from any grain-boundary noise, or capable of producing large-sized material relatively easily. As a method of manufacturing a thin film of such amorphous alloy, a sputtering method of causing ions to collide with a target to form a thin film on a substrate positioned near the target is often used.
Among the materials for a target used in the sputtering, there has been proposed, for example, a mixed structure composed of a phase of intermetallic compound of rare earth element and transition metal and a phase of transition metal alone, having features of (1) less cracking and (2) satisfactory uniform composition (Japanese Laid-Open Patent Application No. Sho 62-70550).
However, the target material involves drawbacks such as (1) composition of the film obtained is greatly different from that of the target, (2) permeability is so high that only a small magnetic flux leaks from the surface of the target, resulting in a low sputtering efficiency and thereby a reduced efficiency of use of the target, especially when a magnetron sputtering device is employed and (3) the surface of the target shows remarkable change in the shape regarding (2) above, which causes change in composition of the film with lapse of sputtering time.
The present inventors have made earnest study for overcoming such problems and obtaining such a target as (1) being less cracking, (2) capable of providing satisfactory uniform composition of the film, (3) having less difference in the composition between the film and the target, (4) capable of achieving a high efficiency of using the target and (5) causing no change in the composition of the resultant film with lapse of sputtering time, and have accomplished the present invention on the finding that the foregoing object can be attained by incorporating, into the structure of a target, not a phase of transition metal alone but a fine mixed phase of rare earth element and intermetallic compound of rare earth element and transition metal.